[DRBD-user] What is exact moment of split brain?

Lars Ellenberg lars.ellenberg at linbit.com
Mon May 11 11:51:41 CEST 2009


On Wed, May 06, 2009 at 08:03:25PM +0530, himanshu padmanabhi wrote:

...
>         net {
>                 allow-two-primaries;
>         }
...

> service drbd start
> drbdadm adjust res1(on both sides)
> drbdadm primary res1(on both sides)
> 
> Then *on local primary side*,
> pvcreate /dev/drbd0
> vgcreate drbdtest /dev/drbd0
> lvcreate -n drbdlv1 -L 50M drbdtest
> 
> Then,on *remote primary side*,I took snapshot
> lvcreate -S -n snap_drbdlv1 -L 50M /dev/drbdtest/drbdlv1
> 
> I am using 'drbd-8.3.0' on 'CentOS 2.6.18-92.el5' machines.
> 
> *My problem*
> I tested above similar scenarios like above,I got split brain error at
> different intervals.

> So I am totally confused @ exact event of split brain.

"What is exact moment of split brain?"

The moment two Primaries lose the communication link.

Or the moment when one node becomes Primary without communication,
while the other node has been Primary without communication.

"What is exact moment split brain _is detected_?"

The moment when communication is resotred
after a split brain situation occurred.

hth,

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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